<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>


<body>
  <div id="app">
    <transition name="fade">
      <span :key="show">{{showNum}}</span>
    </transition>
  </div>

  <script>
    var vm = new Vue({
      el: "#app",
      data: {
        show: "A",
      },
      computed: {
        showNum() {
          switch (this.show) {
            case "A":
              return "我是A";
            case "B":
              return "我是B";
            case "C":
              return "我是C";
          }
        }
      }
    })
  </script>
</body>

</html>